(Java Web) 提交表单 实例讲解

开门见山，一张图解释

首先设置表单的

此处的action对应web.xml中的url-pattern web.xml中需要注册好对应的Servlet

method可设置post 或者 get不设置的话默认是get

后文添加的其他文件的web.xml注册代码不在展示

	
		姓名
		 

		爱好 
		 阅读
		 跑步
		 音乐

		该课程名称
        Java Web
        Android
        PHP

		交卷请单击：
		重答请单击：
	

  000
  
    index.html
    index.htm
    index.jsp
    default.html
    default.htm
    default.jsp
  
  
   
    Register
    test.com.Register
  
  
    Register
    /myURL/*
  

访问index:http://localhost:8080/000/index.html

package test.com;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.Map;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Register extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    public Register() {
        super();
    }

	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
			throws ServletException, IOException {
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) 
			throws ServletException, IOException {
		//解决中文乱码,设置字符编码
		request.setCharacterEncoding("utf-8");
		
		//request存储的是一个键值对，key:String val:String[]
		
		//getParameter 根据键获得值
		String name = request.getParameter("name");
		System.out.println("name=" + name);
		//空值为null
		String age = request.getParameter("age");
		System.out.println("age=" + age);
		
		System.out.println("********************");
		
		//枚举类型，获得请求参数的列表
		Enumeration pNames = request.getParameterNames();
		while(pNames.hasMoreElements()){
			String pname = pNames.nextElement();
			//如果参数名称的值有多个，则获取第一个
			String namevalue = request.getParameter(pname);
			System.out.println(pname + "=====" + namevalue);
		}
		
		System.out.println("********************");
		
		//一般用于获取复选框
		String[] pValues = request.getParameterValues("hobby");
		for (String hobby : pValues){
			System.out.println(hobby);
		}
		
		System.out.println("********************");
		
		//获得所有键值对
		Map pMap = request.getParameterMap();
		//获得所有键
		Set keySet = pMap.keySet();
		for (String mpname : keySet){
			String[] values = pMap.get(mpname);
			System.out.print(mpname + "===");
			for (String value : values){
				System.out.print(value + " ");
			}
			System.out.println();
		}
	}

}

name=张三
age=null

---

name=张三
hobby=read
course=====Java Web

---

read
run
music

---

name=张三
hobby=read run music
course===Java Web

设置字符集，放置中文导致的乱码

request.setCharacterEncoding(“utf-8”);

根据参数key获得val，如果没有该键值对接受内容为null

String name = request.getParameter(“name”);

枚举类型，获得请求参数的列表

Enumeration pNames = request.getParameterNames();

一般用于获取复选框 用String[]形式接受

String[] pValues = request.getParameterValues(“hobby”);

获得所有键值对

Map pMap = request.getParameterMap();

第一个Servlet

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取对象
		String name = request.getParameter("name");
		String age = request.getParameter("age");
		
        //理解上可以类比成一个Map
        
		//放入requset的域属性中
		//作用域就是一次请求的时间
		request.setAttribute("name", name);
		request.setAttribute("age", age);
		
		//删除属性
		request.removeAttribute("age");
		
		//当前请求转发到另一个Servlet中（还是在Servlet中没有返回浏览器，算这一次请求）
		request.getRequestDispatcher("/otherServlet").forward(request, response);
	}

第二个Servlet

	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
			throws ServletException, IOException {
		//设置字符集
		response.setContentType("text/html;charset=utf-8");
		request.setCharacterEncoding("utf-8");
		
		//获取从另一个Servlet中传入的数据
		String name = (String)request.getAttribute("name");
		String age = (String)request.getAttribute("age");
		System.out.println("name = " + name);
		System.out.println("age = " + age);
		
		//字符集要在生成PrintWriter对象之前使用
		PrintWriter out = response.getWriter();
		
		out.println("可放html代码");		//也要处理乱码
		out.append("show code");
		out.println();		//只是空格
		out.print("
");	//真换行	
		out.print("name = " + name);
		out.print("
");
		out.write("age = " + age);
		
//		再次跳转 可以跳转到html的页面
//		request.getRequestDispatcher("/welcome.html").forward(request, response);
	}

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		StringBuffer requestURL = request.getRequestURL();
		System.out.println("requestURL == " + requestURL);
		//资源路径
		String requestURI = request.getRequestURI();
		System.out.println("requestURI == " + requestURI);
		//获得请求的上下文路径（就是项目名）
		String contextPath = request.getContextPath();
		System.out.println("contextPath == " + contextPath);
		//获取客户端的ip地址
		String remoteAddr = request.getRemoteAddr();
		System.out.println("remoteAddr == " + remoteAddr);
		//Servlet的路径	精确部分，就是在web.xml中设置的url
		String servletPath = request.getServletPath();
		System.out.println("servletPath == " + servletPath);
		//URI中去掉精确部分
		String pathInfo = request.getPathInfo();
		System.out.println("pathInfo == " + pathInfo);
		//请求的方式 GET或者POST
		String method = request.getMethod();
		System.out.println("method == " + method);
	}

输出

这里以本文开头图片中的表单的url提交，注意文本代码所在的项目名是000

​ 项目名 url的精确部分 非精确部分

URI = ServletContext + ServletPath + PathInfo

requestURL == http://localhost:8080/000/myURL/toText
requestURI == /000/myURL/toText
contextPath == /000
remoteAddr == 0:0:0:0:0:0:0:1
servletPath == /myURL
pathInfo == /toText
method == POST